/*-----------------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_fir_interpolate_q15.c
*
* Description:	Q15 FIR interpolation.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* ---------------------------------------------------------------------------*/

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Interpolate
 * @{
 */

/**
 * @brief Processing function for the Q15 FIR interpolator.
 * @param[in] *S        points to an instance of the Q15 FIR interpolator structure.
 * @param[in] *pSrc     points to the block of input data.
 * @param[out] *pDst    points to the block of output data.
 * @param[in] blockSize number of input samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
 * Lastly, the accumulator is saturated to yield a result in 1.15 format.
 */

#ifndef ARM_MATH_CM0

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_interpolate_q15(
    const arm_fir_interpolate_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	q15_t* pState = S->pState;                     /* State pointer                                            */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
	q15_t* pStateCurnt;                            /* Points to the current sample of the state                */
	q15_t* ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
	q63_t sum0;                                    /* Accumulators                                             */
	q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
	uint32_t i, blkCnt, j, tapCnt;                 /* Loop counters                                            */
	uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
	uint32_t blkCntN2;
	q63_t acc0, acc1;
	q15_t x1;

	/* S->pState buffer contains previous frame (phaseLen - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + ((q31_t) phaseLen - 1);

	/* Initialise  blkCnt */
	blkCnt = blockSize / 2;
	blkCntN2 = blockSize - (2 * blkCnt);

	/* Samples loop unrolled by 2 */
	while(blkCnt > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;
		*pStateCurnt++ = *pSrc++;

		/* Address modifier index of coefficient buffer */
		j = 1u;

		/* Loop over the Interpolation factor. */
		i = (S->L);

		while(i > 0u) {
			/* Set accumulator to zero */
			acc0 = 0;
			acc1 = 0;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (S->L - j);

			/* Loop over the polyPhase length. Unroll by a factor of 4.
			 ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
			tapCnt = phaseLen >> 2u;

			x0 = *(ptr1++);

			while(tapCnt > 0u) {

				/* Read the input sample */
				x1 = *(ptr1++);

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Perform the multiply-accumulate */
				acc0 += (q63_t) x0 * c0;
				acc1 += (q63_t) x1 * c0;


				/* Read the coefficient */
				c0 = *(ptr2 + S->L);

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += (q63_t) x1 * c0;
				acc1 += (q63_t) x0 * c0;


				/* Read the coefficient */
				c0 = *(ptr2 + S->L * 2);

				/* Read the input sample */
				x1 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += (q63_t) x0 * c0;
				acc1 += (q63_t) x1 * c0;

				/* Read the coefficient */
				c0 = *(ptr2 + S->L * 3);

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += (q63_t) x1 * c0;
				acc1 += (q63_t) x0 * c0;


				/* Upsampling is done by stuffing L-1 zeros between each sample.
				 * So instead of multiplying zeros with coefficients,
				 * Increment the coefficient pointer by interpolation factor times. */
				ptr2 += 4 * S->L;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
			tapCnt = phaseLen % 0x4u;

			while(tapCnt > 0u) {

				/* Read the input sample */
				x1 = *(ptr1++);

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Perform the multiply-accumulate */
				acc0 += (q63_t) x0 * c0;
				acc1 += (q63_t) x1 * c0;

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* update states for next sample processing */
				x0 = x1;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* The result is in the accumulator, store in the destination buffer. */
			*pDst = (q15_t)(__SSAT((acc0 >> 15), 16));
			*(pDst + S->L) = (q15_t)(__SSAT((acc1 >> 15), 16));

			pDst++;

			/* Increment the address modifier index of coefficient buffer */
			j++;

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 2;

		pDst += S->L;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 2, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blkCntN2;

	/* Loop over the blockSize. */
	while(blkCnt > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;

		/* Address modifier index of coefficient buffer */
		j = 1u;

		/* Loop over the Interpolation factor. */
		i = S->L;

		while(i > 0u) {
			/* Set accumulator to zero */
			sum0 = 0;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (S->L - j);

			/* Loop over the polyPhase length. Unroll by a factor of 4.
			 ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
			tapCnt = phaseLen >> 2;

			while(tapCnt > 0u) {

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Upsampling is done by stuffing L-1 zeros between each sample.
				 * So instead of multiplying zeros with coefficients,
				 * Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += (q63_t) x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += (q63_t) x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += (q63_t) x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += (q63_t) x0 * c0;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
			tapCnt = phaseLen & 0x3u;

			while(tapCnt > 0u) {
				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += (q63_t) x0 * c0;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* The result is in the accumulator, store in the destination buffer. */
			*pDst++ = (q15_t)(__SSAT((sum0 >> 15), 16));

			j++;

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 1;

		/* Decrement the loop counter */
		blkCnt--;
	}


	/* Processing is complete.
	 ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	i = ((uint32_t) phaseLen - 1u) >> 2u;

	/* copy data */
	while(i > 0u) {
#ifndef UNALIGNED_SUPPORT_DISABLE

		*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
		*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;

#else

		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

		/* Decrement the loop counter */
		i--;
	}

	i = ((uint32_t) phaseLen - 1u) % 0x04u;

	while(i > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		i--;
	}
}

#else

/* Run the below code for Cortex-M0 */

void arm_fir_interpolate_q15(
    const arm_fir_interpolate_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	q15_t* pState = S->pState;                     /* State pointer                                            */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
	q15_t* pStateCurnt;                            /* Points to the current sample of the state                */
	q15_t* ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
	q63_t sum;                                     /* Accumulator */
	q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
	uint32_t i, blkCnt, tapCnt;                    /* Loop counters                                            */
	uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */


	/* S->pState buffer contains previous frame (phaseLen - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + (phaseLen - 1u);

	/* Total number of intput samples */
	blkCnt = blockSize;

	/* Loop over the blockSize. */
	while(blkCnt > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;

		/* Loop over the Interpolation factor. */
		i = S->L;

		while(i > 0u) {
			/* Set accumulator to zero */
			sum = 0;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (i - 1u);

			/* Loop over the polyPhase length */
			tapCnt = (uint32_t) phaseLen;

			while(tapCnt > 0u) {
				/* Read the coefficient */
				c0 = *ptr2;

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *ptr1++;

				/* Perform the multiply-accumulate */
				sum += ((q31_t) x0 * c0);

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* Store the result after converting to 1.15 format in the destination buffer */
			*pDst++ = (q15_t)(__SSAT((sum >> 15), 16));

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 1;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Processing is complete.
	 ** Now copy the last phaseLen - 1 samples to the start of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	i = (uint32_t) phaseLen - 1u;

	while(i > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		i--;
	}

}

#endif /*   #ifndef ARM_MATH_CM0 */


/**
 * @} end of FIR_Interpolate group
 */
